top of page


 Based on the collector system, solar water heaters can be of two types.


Flat Plate Collectors (FPC) based Solar Water Heaters

The  solar radiation  is  absorbed  by  Flat  Plate  Collectors  which  consist  of  an insulated  outer metallic  box  covered  on  the  top  with  glass  sheet. Inside  there  are blackened  metallic  absorber  (selectively  coated)  sheets with  built  in  channels  or  riser tubes to carry water. The absorber absorbs the solar radiation and transfers the heat to the flowing water.

Evacuated Tube Collectors (ETC) based Solar Water Heaters

Evacuated  Tube  Collector  is  made  of  double  layer  borosilicate  glass  tubes evacuated  for  providing  insulation.  The  outer  wall  of  the  inner  tube  is  coated  with selective  absorbing  material. This  helps  absorption  of  solar  radiation  and  transfers  the heat to the water which flows through the inner tube.

Solar water heating is now a mature technology.  Wide spread utilization of solar water heaters can reduce a significant portion of the conventional energy being used for heating water in homes, factories and other commercial and institutional establishments.  Internationally  the  market  for  solar  water  heaters  has  expanded  significantly  during  the last decade.


Salient Features of Solar Water Heating System 


Solar Hot Water System turns cold water into hot water with the help of sun’s rays.   


  •  Around  60  deg.  –  80  deg.  C  temperature  can  be  attained  depending  on  solar radiation, weather conditions and solar collector system efficiency.


  • Hot water for homes, hostels, hotels, hospitals, restaurants, dairies, industries etc.


  • Can be installed on roof-tops, building terrace and open ground where there is no shading, south orientation of collectors and over-head tank above SWH system


  • SWH  system  generates  hot  water  on  clear  sunny  days  (maximum),  partially clouded (moderate) but not in rainy or heavy overcast day


  • Only soft and potable water can be used


  • Stainless  Steel  is  used  for  small  tanks  whereas  Mild  Steel  tanks  with  anti-corrosion coating inside are used for large tanks


  • Solar  water  heaters  (SWHs)  of  100-300  litres  capacity  are  suited  for  domestic application.


  • Larger  systems  can  be  used  in  restaurants,    guest  houses,  hotels,  hospitals, industries etc.


Fuel Savings :

A 100 litres capacity SWH can replace an electric geyser for residential use and saves 1500 units of electricity annually.


Avoided uitility cost on generation:
The use of 1000 SWHs of 100 litres capacity each can contribute to a peak load shaving of 1 MW.

Environmental benefits:

A  SWH  of  100  litres  capacity  can  prevent  emission  of  1.5  tonnes  of  carbon- dioxide per year.


Life : 15-20 years

Approximate Cost :  Rs.14000- 19,000 for a 100 litres capacity system and

                                                             Rs.110-150 per installed litre for higher capacity systems

Payback period :           3-4 years when electricity is replaced

                                                      4-5 years when furnace oil is replaced

                                                      5-6 years when coal is replaced

bottom of page